Bummer. I have no idea what to tell you to try next with that controller. There is some other not so obvious damage.

Some time ago back when I thought building computers and overclocking them was fun. I was installing a P3 Tualatin CPU with a big cooling tower and fan on a favorite Motherboard that handled being overclocked very well when the screwdriver slipped..... Well I had to use a magnifying glass to see the almost microscopic grain of sand devise that had been knocked loose... And NOPE that motherboard never booted up again!

I can say that if you absolutely do not want to re-cable the cart for reasons related to expense or effort & time... that the cart's performance will still be improved significantly by the XCT400 install.
However... I have tested the research carts here at the Carts Unlimited research Lab & the best performance won't be had until the cables are all upgraded.